This invention relates generally to a probe apparatus, such as an ultrasound transesophageal probe for insertion to the stomach via the mouth and throat for subsequent manipulation, by means of a wire system, for imaging the heart and other internal bodily organs. Such apparatus is well-known in the art. A key requirement for such a probe is that the wire control system must enable movement of the head of the probe over a wide range of positions with as small a radius of curvature as possible.
The internal probe mechanism, including the external electrical leads and control wires of such a system, must be completely insulated from bodily contact by a surrounding jacket or boot. However, the completed probe apparatus, typically comprising an articulate mechanism, 124 coaxial cables connected to two transducers, and the aforementioned jacket or boot, is a relatively rigid system that puts enormous strain on the wire control system commonly leading to excessive fatigue and premature failure. Such probe apparatuses, which may cost up to $30,000-40,000, often experience premature failure after just a few thousand activations due to control wire fatigue. For economy and efficiency, it is desirable to increase the useful life of these probes by tenfold or more.
In general, it is well-known in the art to use sleeves, boots or jackets of various types in connection with a wide range of medical instruments that are intended to be utilized inside the body. Such sleeves, boots or jackets may be variously employed to facilitate insertion of the instrument into the body, to shield the body from the instrument and vice versa, to supply fluid to an internal site, and many other such applications. In some of these applications, the prior art teaches the use of a catheter wherein at least some portion of the catheter includes a plurality of apertures in the side wall of the catheter. In these devices, however, the apertures serve no function other than to permit drainage of fluid from the body through the catheter or, alternatively, for supplying fluid through the catheter to some internal body site.
Representative of this type of prior art are U.S. Pat. Nos. 1,786,373 (Walker--note FIG. 1, apertures 20); 3,595,241 (Sheridan--note FIG. 1, apertures 12); 3,905,361 (Hewson et al.--note FIG. 1, apertures 3); 4,748,984 (Patel--note FIGS. 1 and 2, apertures 29); 4,781,678 (de Couet et al.--note FIGS. 1, 2 and 3, apertures 4); 4,804,358 (Karcher et al.--FIG. 1, apertures 18); 4,813,929 (Semrad--FIG. 6, apertures in chest tube 20; FIG. 7, apertures 38); 4,955,384 (Taylor et al.); 4,990,133 (Solazzo--FIG. 1, drainage orifices 16; FIG. 2, irrigation ports 25). It should be noted that there is no suggestion in these patents of a need for greater flexibility in the catheter systems, nor is there any teaching of employing
the inner catheter of a double-catheter system in order to increase flexibility.
U.S. Pat. No. 4,291,694 (Chai) is directed to another type of catheter apparatus used in connection with thoracic surgery. Pneumotube 10 (FIG. 1) includes a proximal portion 11 having a plurality of rows of small apertures 14. According to Chai, the size and arrangement of apertures 14 should be selected such that this portion of the pneumotube "will have sufficient rigidity . . . but also have sufficient flexibility to conform to the chest wall as the patient's lung expands, "(col. 3, lines 54-61).
U.S. Pat. No. 4,661,094 (Simpson) is directed to a perfusion catheter for positioning in a partially occluded blood vessel. Tubular member 16 (FIGS. 2 and 3) is provided with a plurality of holes 24 that "are spaced apart longitudinally . . . and are also spaced circumferentially . . . " (col. 2, lines 15-17). More particularly, "each successive hole is offset by 90 degrees with respect to the preceding hole," (col. 2, lines 26-27). The purpose of the 90 degree offset configuration in Simpson is clearly to facilitate drainage. There is no suggestion in Simpson that this aperture configuration has any beneficial effects with respect to flexibility. There is also no teaching in Simpson of a double catheter system.
U.S. Pat. No. 4,576,772 (Carpenter) is directed to a multi-lumen catheter having filled "notches" (FIG. 1, notches 17; FIG. 2, filled notches 19) to add greater flexibility to the catheter. Specifically, the notches in the Carpenter catheter are filled "with a vulcanizable polymer material having a hardness when cured less than the hardness of said plastic tube whereby the resistance to bending of said tube is reduced" (col. 1, lines 55-58). Carpenter requires that the notches be filled in order to maintain a fluid-tight catheter (col. 1, lines 47-48 and 65-66). Carpenter uses the multiple lumens of his catheter as ducts or feeding tubes to provide the polymeric filler to the notches (col. 2, lines 42-47). According to Carpenter "[t]he resultant assembly . . . provides an articulatable catheter section or length that flexes readily with less stress and strain on the control wires as they are operated to deflect the distal end of the scope with which the catheter is used," (col. 2, lines 63-68). But, the Carpenter catheter is a relatively inexpensive and disposable system that is neither designed for nor capable of accommodating an articulate mechanism and 124 coaxial instrumentation cables as required for an ultrasonic probe apparatus. Thus, nothing in the Carpenter patent suggests how to overcome the rigidity problem associated with ultrasonic probes or teaches how to increase the useful life of these extremely expensive devices by minimizing premature fatigue of the control system.
Some of the more common approaches to the general problem of increasing flexibility in a tubular system have proven completely inapplicable to the specific case of a transesophageal probe. For example, flexibility of the probe system could be increased by using larger, looser-fitting sleeves or a bellows-style sleeve construction to contain the articulate mechanism, control wires, and 124 coaxial cables. The trade-off, however, is that the resultant system would be larger in diameter and, therefore, more difficult to insert through the esophagus. Similarly, a tight, slippery outer surface makes it easier to insert the probe, whereas a loose or bellows-style surface would impede insertion. Sleeves comprising concentric or articulated ring structures could also be used to increase flexibility, but again only at the cost of unacceptably increasing the size of the device and decreasing the ease with which the device can be inserted.
These and other problems with and limitations of the prior art transesophageal probes are overcome with the flexible probe system of this invention.